I just purchased a new 2018 RT188 with a Merc 115 four stroke with command thrust. It came with a 20p laser II. During my initial break-in, my WOT was getting close to 6700 rpms trim up but not slipping. To be safe, I trim down the boat at WOT in order to maintain 6300 during the one minute WOT runs. I’m thinking that it’s possibly a bad RPM gauge. Has anyone had this issue? Also, do these engines have rev limiters? I appreciate any info you guys may have...
Congrats on the new boat! Not sure why they put that prop on a CT lower unit? I didn't even know it would fit. I have that prop on my regular 2017 lower unit. Without a jack plate I can't turn it to the limiter. They do have a limiter. It would have cut you off at 6300 RPM's
https://www.mercurymarine.com/en/us/...15-150-pro-xs/
I doubt it is a bad tach. You may just need to adjust the pole setting to the 4 stroke. I am not sure which setting?
Most of the CT 115 Pro XS 4s I've seen on a RT had a 23 Tempist. The non CT came with the 20 Laser II.
Thank you for the info. I will look into the tach. I made contact with the dealer and they are going to send me a new prop. Want know which prop until Monday. I hope it’s the 23 tempest. The hub on the laser II does not seem to be large enough for the foot. I will attach a pic...
If they put the small hub Laser2 on a CT lower unit you are probably leaking a lot of exhaust around the prop. This would cause cavitation and would explain the high RPMs at WOT.
If you're really turning 6700 RPM you should be on the limiter so the tach is probably off too.
Thank you for the reply. Yes, they did put a small hub prop on the boat. I tried to post a picture of it, but can’t figure out how to do it on this site.
My RT188 115 CT came with a Tempest Plus 21P. I get close to 50 although I seldom push it that hard.
Thank you for the info. Do you also have the Pro XS?
If I were you I would invest the money into a Smart Craft gauge for that motor. It will give you an accurate RPM plus a whole host of other data streams you can look at to monitor the health of your engine. You wouldn't be revving that engine out that high as the rev limiter would kick in and keep you under the max RPM. During the WOT run go ahead and trim it up to let her eat. You want that engine to get hot then cool back down as building heat will help with seating the rings. This would also be a good post to have in the Mercury 4 stroke forum. Be sure to include your serial number and Don Weed will comment....he's the "Yoda" of Mercury engines.
You're Welcome. I have an early 2017 115 Pro XS 4S. I bought the boat they used at the Ranger Dealer meeting that year. Ranger didn't start putting the CT lower units on them until later in 2017. I agree on the Smart Craft for a variety of reasons. I had the SC1000 tach added to mine before I ever brought it home.Originally Posted by z20 fatboy
Thanks guys. I will look into the Smart Craft gauge. I was also looking into
the Vessel View Link with a Lowrance in the console. In regards to the prop, they are replacing the laser II with a Tempest 21p as this is what Ranger recommends...
Yes it’s a 2018 Prox XS
I have the same hull and motor with the ct lower and the 21p tempest works great for me.
I have the same hull and motor with the ct lower and the 21p tempest works great for me.
Hi Mr. Derek, did you have to remove the plastic sleeve inside the gear case for the Tempest to fit? I tried to install my new Tempest and it rubs the plastic sleeve. Mercury said that it was ok to remove it. Just curious if you had the same issue.
Z20 fatboy I see that you are from BHam. Take your boat buy Airport Marine in Alabaster. You have the wrong prop.
2023 Triton 18TRX
2023 Mercury 200 Pro XS
80# Ultrex IPilot Link
Helix 12 Mega SI & Garmin Livescope w/ 1242XSV GPSmap
You are probably correct, but ranger recommended the Tempest 21p. Also, mercury stated that the prop is a good choice for the command thrust 115 and RT188. I pulled out the cheap plastic sleeve and re-installed the prop. Seems to fit perfect now. I will try it out as soon as it stops raining.. By the way, I really like the green fusion. I ended up getting a left over white 2018 from a Mississippi dealer. Airport only had or has the RT188C boat in 2018’s. It has the coin box that Airport said was not available in any RT188.
Mine still has the plastic ring. It rubs slightly and it has come unclipped a couple times. Last time I had the prop off I bent the clips to see if it stays in better. If not its going in the trash.
Mine still has the plastic ring. It rubs slightly and it has come unclipped a couple times. Last time I had the prop off I bent the clips to see if it stays in better. If not its going in the trash.
When I pulled the prop off, the sleeve came out stuck to the prop.
Mine came shipped from the factory with the 21 tempest. The Laser II is only for use on the none CT gearcase.
2023 Triton 18TRX
2023 Mercury 200 Pro XS
80# Ultrex IPilot Link
Helix 12 Mega SI & Garmin Livescope w/ 1242XSV GPSmap
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